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Friday, 14 September 2012

The London Slaty-backed Gull: update

Rewind to this day 20 months ago: Britain's first Slaty-backed Gull, at Rainham landfill, Greater London.

Exactly one year and eight months ago to the day, I was out on my local patch, sitting on a huge pile of earth and rubbish in steady drizzle, happy as Larry. Why? Imagine wiping the raindrops off your scope eyepiece, lowering your head, and focusing: there, in among the throngs of gulls on an unpleasant January afternoon, was Britain’s first Slaty-backed Gull, settled, preening, and giving excellent views.

That was actually the last time I saw the bird, only about 24 hours after I'd found it. Others got lucky in the weeks that followed, but I only ever did manage to see it on those first two days.

A long time passed before I finally submitted the record, having done all the research I felt necessary for such a bird. That lengthy submission and a series of photos are still doing the rounds with the Rarities Committee, but those interested in this Pacific vagrant might like to know that I’ve just submitted a supplementary note on the record.

In brief, it relates to new evidence provided by Peter Adriaens about the variability in the darkness of this species’ upperparts – the main talking point of the London bird, with some believing it was not dark enough. Peter visited Japan earlier in the year and spent two weeks watching and photographing gulls at Chosi. Images from his trip, now uploaded online and with informative captions, show that, in his words, “variation in mantle colour does not necessarily reflect hybridisation, but is also simply age-related”. He also addresses the question of hybrids, believing they should show more than one anomalous trait. The image galleries are viewable here: